“They’ll give a warning. They’ll tell them to put the firearm down or drop the knife. If they can give that warning and if they can’t, they have to make that decision to use their firearm,” Boehm said.

Boehm said that the main consideration is stopping the threat.

“It doesn’t matter if you’re in the subway or if you’re on a crowded street like in Times Square or by the Empire State Building. If the officers are being threatened with deadly physical force, the officers are allowed to use deadly physical force,” he said.

The fact that bystanders were also injured will make Friday morning’s shooting a case that will be debated for a long time to come.

Police said too many residents and tourists get in the way, watching or getting video instead of running for cover as soon as these situations start.

Experts want residents and tourists to know how to run for cover as soon as a situation like what happened on Friday starts and not get in the way of officers to rubberneck or take their own videos.